A security barrier or bollard may be used for resisting an unauthorised passage of a vehicle such as a car or a lorry. Such barriers typically comprise a support with a barrier member or post mounted to it. The support may be cast into concrete foundations below ground level, or it may be surface mounted above the ground level. The barrier member or post is typically arranged to be retractable so that it can be stowed relative to the support to allow the vehicle to pass, or deployed to a working position to prevent or inhibit the vehicle to pass.
In different countries the security barrier or bollard may be required to comply with various parameters. Such parameters may relate to various dimensions for the security barrier or bollard. One such parameter may be that a maximum gap between bollards may not be more than 1.2 m. Defining such a maximum gap may provide an assurance that a vehicle wider than 1.2 m cannot simply drive between the bollards. Another parameter may be that a minimum gap between movable parts of the security barrier or bollard is not less than 0.4 m, which may be particularly relevant in the case of powered movable parts of the security barrier or bollard. Defining such a minimum gap may provide the advantage of reducing the possibility for people or objects to become trapped by the movable parts, which may provide an assurance that the security barrier or bollard is effective and safe to operate.
Security barriers or bollards are typically provided in two categories. The first category is a high security barrier, or anti-terrorist barrier, that is intended to prevent a vehicle from passing. Such a barrier is robustly constructed and is typically about 1-1.5 meters above ground level. A high security barrier might be used at a road entrance to an airport or an official building, such as a Government building, and is typically able to withstand a crash impact from a car or lorry. The second category of security barrier might be used at a home or work premises to safeguard a car parking space or driveway from being used by an unauthorised vehicle. Such barriers are relatively less robustly constructed, and may extend up to one meter above ground level.
It is known to provide a security bollard or post which is pivotable on a support between a vertical position and a horizontal position. The support may be surface mounted on the ground, or it may be cast into a concrete foundation within the ground. Such arrangements have the disadvantage that the security bollard or post may form a trap hazard with the ground as it moves to the stowed position, which may represent a safety risk.
It is also known to provide a security bollard or post which is movable relative to a housing between a vertical position above ground and a vertical position below ground. Such arrangements have the problem of requiring a deep foundation for the housing for the post, which must be at least as deep as the height of the bollard above ground. Using such a deep foundation is disadvantageous, particularly in an urban environment, because it may interfere with services such as power lines, drains, or communication cables. In an alternative arrangement the post is telescopic so that the foundations for the housing are not required to be as deep. Such security bollards or posts generally represent less of a safety hazard than the pivotable security bollard or post because there is no trap hazard, but they may be more costly and complex.
It is broadly an object of the present invention to address one or more of the above mentioned disadvantages of previously known security barriers.